1. Field of the Invention
The present invention relates to a semiconductor device.
2. Description of the Related Art
A charge trap type nonvolatile semiconductor memory using a charge storage insulating film for charge trap as a charge storage layer has been proposed (e.g., see Jpn. Pat. Appln. KOKAI Publication No. 2004-158810). In the foregoing charge trap type nonvolatile semiconductor memory, a charge injected to a charge storage insulating film via a tunnel insulating film is trapped in a trap level of the charge storage insulating film. In this way, charges are stored in the charge storage insulating film. Typically, a MONOS or SONOS type nonvolatile semiconductor memory has been known as the charge trap type nonvolatile semiconductor memory.
However, the foregoing charge trap type nonvolatile semiconductor memory has a problem of current characteristic deterioration. For example, leak current resulting from the following factors is given as a problem. One of the factors is concentration of electric line of force at the end portion of a gate structure. The other is process damage (etching damage) at the sidewall of a gate structure.